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tty flush flip buffer on ldisc input queue flush

PATCH New Paul Fulghum 4 participants 4 messages May 7, 2007 – Jan 4, 2008 Char and misc drivers

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Paul Fulghum

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#0 lore raw

PATCH 1/1 tty flush flip buffer on ldisc input queue flush

Flush the tty flip buffer when the line discipline input queue is flushed, including the user call tcflush(TCIFLUSH/TCIOFLUSH). This prevents unexpected stale data after a user application calls tcflush().

Cc Alan Cox <[email protected]>
Cc Antonino Ingargiola <[email protected]>
Signed-off-by Paul Fulghum <[email protected]>
drivers/char/tty_io.c +33 -0
@@ -365,6 +365,29 @@ static void tty_buffer_free(struct tty_s
 }
 
 /**
+ *	tty_buffer_flush		-	flush full tty buffers
+ *	@tty: tty to flush
+ *
+ *	flush all the buffers containing receive data
+ *
+ *	Locking: none
+ */
+
+static void tty_buffer_flush(struct tty_struct *tty)
+{
+	struct tty_buffer *thead;
+	unsigned long flags;
+
+	spin_lock_irqsave(&tty->buf.lock, flags);
+	while((thead = tty->buf.head) != NULL) {
+		tty->buf.head = thead->next;
+		tty_buffer_free(tty, thead);
+	}
+	tty->buf.tail = NULL;
+	spin_unlock_irqrestore(&tty->buf.lock, flags);
+}
+
+/**
  *	tty_buffer_find		-	find a free tty buffer
  *	@tty: tty owning the buffer
  *	@size: characters wanted

@@ -1240,6 +1263,7 @@ void tty_ldisc_flush(struct tty_struct *
 			ld->flush_buffer(tty);
 		tty_ldisc_deref(ld);
 	}
+	tty_buffer_flush(tty);
 }
 
 EXPORT_SYMBOL_GPL(tty_ldisc_flush);

@@ -3336,6 +3360,15 @@ int tty_ioctl(struct inode * inode, stru
 		case TIOCMBIC:
 		case TIOCMBIS:
 			return tty_tiocmset(tty, file, cmd, p);
+		case TCFLSH:
+			switch (arg) {
+			case TCIFLUSH:
+			case TCIOFLUSH:
+				/* flush tty buffer and allow ldisc to process ioctl */
+				tty_buffer_flush(tty);
+				break;
+			}
+			break;
 	}
 	if (tty->driver->ioctl) {
 		retval = (tty->driver->ioctl)(tty, file, cmd, arg);
#1 lore raw

PATCH 1/1 isdn/i4l: 'NO CARRIER' message lost after ldisc flush

The ISDN tty layer doesn't produce a 'NO CARRIER' message after hangup.

I suppose it broke when tty_buffer_flush() has been added to tty_ldisc_flush() in the commit below.

For isdn_tty_modem_result(RESULT_NO_CARRIER..) the message inserted via isdn_tty_at_cout() -> tty_insert_flip_char() is flushed immediately by tty_ldisc_flush() -> tty_buffer_flush(). More annoyingly, the audio abort sequence DLE-ETX is also lost.

This patch fixes only active audio connections, because I assume that nobody changes the line discipline for audio.

For non-audio connections the problem remains.
Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result() at all because it's done at tty_close?

Quoted 16 lines · Paul Fulghum

Flush the tty flip buffer when the line discipline input queue is flushed, including the user call tcflush(TCIFLUSH/TCIOFLUSH). This prevents unexpected stale data after a user application calls tcflush().

Cc Alan Cox <[email protected]>
Cc Antonino Ingargiola <[email protected]>
Signed-off-by Paul Fulghum <[email protected]>
drivers/char/tty_io.c +1 -0
@@ -1240,6 +1263,7 @@ void tty_ldisc_flush(struct tty_struct *
 			ld->flush_buffer(tty);
 		tty_ldisc_deref(ld);
 	}
+	tty_buffer_flush(tty);

[..]

Signed-off-by Matthias Goebl <[email protected]>
drivers/isdn/i4l/isdn_tty.c +5 -0
@@ -2645,7 +2649,12 @@
 		if ((info->flags & ISDN_ASYNC_CLOSING) || (!info->tty)) {
 			return;
 		}
+#ifdef CONFIG_ISDN_AUDIO
+		if ( !info->vonline )
+			tty_ldisc_flush(info->tty);
+#else
 		tty_ldisc_flush(info->tty);
+#endif
 		if ((info->flags & ISDN_ASYNC_CHECK_CD) &&
 		    (!((info->flags & ISDN_ASYNC_CALLOUT_ACTIVE) &&
 		       (info->flags & ISDN_ASYNC_CALLOUT_NOHUP)))) {
#2 lore raw

Re: [PATCH] isdn/i4l: 'NO CARRIER' message lost after ldisc flush

Quoted 3 lines

For non-audio connections the problem remains.
Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result() at all because it's done at tty_close?

I'm not sure I understand why the tty_ldisc_flush is being done in the ISDN layer at this point but this change looks fine to me.

Alan

#3 lore raw

Re: [PATCH] isdn/i4l: 'NO CARRIER' message lost after ldisc flush

From: Alan Cox <[email protected]>
Date: Thu, 3 Jan 2008 22:30:54 +0000

Quoted 6 lines
Quoted 3 lines

For non-audio connections the problem remains.
Maybe we can remove the tty_ldisc_flush() in isdn_tty_modem_result() at all because it's done at tty_close?

I'm not sure I understand why the tty_ldisc_flush is being done in the ISDN layer at this point but this change looks fine to me.

I'll apply this fix to net-2.6 and push to Linus.

Thanks.